Fix deprecated render nothing: true

DEPRECATION WARNING: `:nothing` option is deprecated and will be removed
in Rails 5.1. Use `head` method to respond with empty response body.

app/controllers/application_controller.rb

@@ -25,7 +25,7 @@ def login_required_api
   end
 
   def nothing
-    render(nothing: true)
+    head 200
   end
 
   def logged_in?

spec/controllers/application_controller_spec.rb

@@ -8,7 +8,7 @@
       before_action :login_required
 
       def index
-        render nothing: true
+        head 200
       end
     end
 
@@ -45,7 +45,7 @@ def index
       before_action :current_member
 
       def index
-        render nothing: true
+        head 200
       end
     end
 

spec/controllers/favicon_controller_spec.rb

@@ -13,7 +13,7 @@
     it "should send favicon" do
       expect(Feed).to receive(:find_by).with(feedlink: @feed.link) { @feed }
       expect(controller).to receive(:send_data).with(anything, image_header) {
-        @controller.render nothing: true
+        @controller.head 200
       }
       get :get, feed: @feed.link
     end